Compact disks (CD) and video disks (LD) as information recording media are often available in the form of disk cartridges having the disks accommodated in casings whereupon recording/reproducing machines such as disk players are loaded with the cartridges. The disk players have a drive shaft for driving the disk and a pickup for recording and reproducing bits of information into and from the disk.
To protect these disks against deposition of dust and debris, damages during handling, and temperature influence, the disks are conventionally enclosed in casings. Each casing includes a center aperture located generally at the center of the casing for allowing the drive shaft to extend therethrough to engage the disk annular hub for driving and an access window located radially outward of the center aperture for allowing a pickup to make access to the disk therethrough for recording and reproducing when the disk player is loaded with the cartridge. The casing further includes movable shutters for normally closing the windows when the disk is not used.
For recording or reproducing numerous data for an instant in an optical disk or the like, a plurality of pickups are required and the casing must then be provided with a plurality of access windows through which the pickups can make access to the disk. The shutters are thus required to simultaneously open or close the center and access windows during loaded and unloaded periods of the disk for the purpose of protecting the disk against dust and debris. Various types of shutters have been proposed for simultaneously opening and closing these windows.
Since the shutter is disposed in close proximity to the casing wall, the shutter can contact and rub the casing wall during its operation. In the case of a relatively large shutter for opening and closing a plurality of access windows, a relatively large available contact surface area leads to a relatively large frictional force which in turn, requires a greater force to actuate the shutter for opening and closing. Consequently, several inconvenient problems will arise. The power consumption on the disk drive side for actuating the shutter will be increased. In the case of a disk cartridge designed so as to automatically close the shutter when the cartridge is removed from the disk drive, the automatic shutter closing operation will be less smooth. Additionally, since the shutter can rub and scrape the resinous casing wall, resin chips will scatter within the casing and build up on the disk, providing a potential error source.